About some criteria of efficiency of complex heat-insulating and slagforming mixtures

Abstract

The total thermal conductivity of the complex heatinsulating and slag-forming mixture is calculated taking into account the convective component of the thermal conductivity and thermal conductivity of the liquid oxide solution formed by melting the ingredients of the complex mixture. It was shown that the thermal conductivity of the complex mixture at an application temperature of 1823 K remains at a rather low level of about 18,8 W/(m·K). criteria for the effectiveness of the complex mixture at various stages of its application are formulated, including feeding the mixture into the steel casting ladle, joint feeding into the steel casting ladle and tundish and molds. Direct measurements found that the use of a complex mixture in a steel pouring ladle reduces the rate of metal cooling by one and a half times. The criterion for the effectiveness of the use of the complex mixture in the intermediate ladle as a heat insulator is the level of negative temperature deviation from the average value of a series of consecutive measurements of 4 °C. The criteria for the effectiveness of the complex mixture as a slag former in the tundish are an increase in the concentration of aluminum oxide in the oxide solution with an increase in the number of melts in the series and a decrease in the concentration of iron oxide in the oxide solution to equilibrium values of about 0,5 % by weight. In the presence of a sufficient amount of a liquid oxide solution formed by the components of the complex mixture, carbonization of the liquid metal with free carbon contained in the mixture does not occur.